I was thinking about buying this lens as a relatively lightweight walkabout (compared to my recently sold 300/2.8 anyway). Has anyone used it for occasional bird shots with a 2x tc - opinions seem to vary as to just how good it is at 400mm. BTW the main use would not be with a 2x tc but it would be nice to have that option.
Another possible use would be for the likes of Butterflies, with a MFD of 1.5 metres it could be handy, especially with a 1.4x tc attached, anyone used it for this sort of thing?
Thanks in advance for your feedback.



